This invention relates to fuel injection systems for internal combustion engines and to apparatus for use therein.
Diesel fuel injection systems are known in the prior art for injecting fuel to engine cylinders in proper timed relation to the phase of engine operation, and with a duration and quantity of fuel injection appropriate for the particular engine. However, prior art systems such as that disclosed in U.S. Pat. No. 3,587,547 entitled "Fuel Injection Control System and Apparatus for Use Therein" issued to R. B. Hussey et al, issued June 28, 1971, controlled only the opening of the injector nozzle by limiting, in a flow control circuit, flow of control fluid in only one direction. Therefore, the quantity of fuel injected was only controlled by controlling the duration and rate of opening the injection nozzle. Further, diesel fuel injection systems operate in an environment wherein pressures above 4500 psi and sometimes as high as 10,000 psi are continuously at the fuel injector nozzle. The presence of this high pressure fuel at the injector has been the cause in some instances of injector failure and in other instances leakage of fuel from the injector into the combustion chamber, both undesirable conditions.